Many systems exist for packaging two or more integrated circuit (IC) dice. These multi-die systems provide physical protection to the IC dice, and electrically couple the IC dice to each other and to various external elements. Due to their complexity, fabrication and testing of multi-die systems can be difficult.
A Folded Stack-Chip Scale Package (FS-CSP) attempts to address the foregoing by allowing separate testing of two IC packages prior to coupling. In order to couple the IC packages, a first one of the IC packages is mounted to a first side of a substrate at one end of the substrate. The other end of the substrate is folded over the top of the first IC package to couple the first side of the substrate to the top of the IC package. The second IC package is thereafter coupled to a second side of the substrate above the first IC package.
The folded substrate may present several unsuitable characteristics. First, the folded portion of the substrate exhibits bending stresses that may compromise the integrity of the substrate and of the electrical traces within the substrate. In addition, the relatively long electrical traces within the substrate may exhibit unwanted resistance and resulting voltage drops.